1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device and a method for fabricating the same that decrease a step coverage between color filter layers.
2. Discussion of the Related Art
Demands for display devices have increased with development of an information society. Accordingly, many efforts have been made to research and develop various flat display devices, such as liquid crystal display (LCD), plasma display panel (PDP), electro-luminescent display (ELD), and vacuum fluorescent display (VFD). In particular, liquid crystal display (LCD) devices have been most widely used as a substitute for a cathode ray tube (CRT) because of their advantageous characteristics of thin profile, lightness, and low power consumption. LCD devices have been implemented as display devices for notebook computers, desktop computers, televisions, and the like. One consideration in developing LCD devices is to develop LCD devices having a high quality picture, such as high resolution and high luminance with a large-sized screen, while maintaining lightness, thin profile, and low power consumption.
In general, the LCD device includes an LCD panel for displaying an image and a driver for supplying a driving signal to the LCD panel. In addition, the LCD panel includes first and second substrates attached to each other with a cell gap therebetween, and a liquid crystal layer formed in the cell gap. Further, alignment layers are respectively formed on facing surfaces of the first and second substrates, wherein the alignment layers are rubbed to align the liquid crystal layer.
The first substrate or a TFT array substrate includes a plurality of gate lines arranged along a first direction, a plurality of data lines arranged along a second direction perpendicular to the first direction, a plurality of pixel electrodes arranged in a matrix-type configuration within pixel regions defined by the crossings of the gate and data lines, and a plurality of thin film transistors for switching signals from the data lines to the pixel electrodes based on signals received from the gate lines.
Further, the second substrate or a color filter array substrate includes a black matrix layer, a color filter layer, and a common electrode. The color filter layer includes red, green, and blue color filters, wherein the color filter layer is formed by repetitively positioning the color filters in order of red(R), green(G), and blue(B) within regions corresponding to the pixel regions of the first substrate. Accordingly, the liquid crystal layer controls the intensity of light, and the light passes through the color filter layers of red(R), green(G), and blue(B) to represent color images.
Generally, the color filter layer may be formed in a dye method, a pigment dispersion method, an electro-deposition method, or a print method. In the dye method, an exposure and developing process is applied to a dyeable and photosensitive resin on a substrate, and then a dyeing process is performed thereto with a dyestuff. The pigment dispersion method is classified into one of two types. The first type of pigment dispersion method includes performing an exposure and developing process after depositing a photosensitive substance to which pigment is dispersed. Further, the second type of pigment dispersion method includes etching a polyimide substance having no photosensitivity to which pigment is dispersed using a photoresist.
In the electro-deposition method, a highly polymerized resin is dissolved or dispersed from a solvent, and then extracted to an electrode by electrochemistry. Moreover, the print method prints inks to which a pigment is dispersed onto a resin.
FIG. 1A to FIG. 1D are cross-sectional views illustrating a method for fabricating a color filter substrate according to the related art. In FIG. 1A, chrome/chrome oxide or chrome/chrome nitride/chrome oxide is deposited to form a first layer on an entire surface of a substrate 11 by sputtering. Then, the first layer is patterned by photolithography to form the black matrix layer 12 on the substrate 11 except in regions P1, P2, and P3.
As shown in FIG. 1B, a first color resin 13 is coated on the entire surface of the substrate 11. Then, a mask M is positioned above the first color resin 13, and ultraviolet (UV) rays is irradiated onto the first color resin 13 through the mask M, to thereby selectively expose the first color resin 13. In particular, the mask M includes opening portions corresponding to the region P1. These opening portions have a width the same as a width of the region P1.
As shown in FIG. 1C, portions of the first color resin 13 (shown in FIG. 1B) is removed to form a color filter 13c in the region P1. In particular, portions of the color resin 13 that are along the edges of the black matrix layer 12 (shown in FIG. 1B) are irradiated by the ultraviolet rays due to diffraction and interference of the ultraviolet rays caused by edges of the mask's opening portions. Thus, the color filter 13c overlaps the black matrix layer 12 along the edges of the black matrix layer 12, thereby forming an uneven substrate surface.
Although not shown, second and third color resins subsequently are coated and are selectively removed, as shown in FIGS. 1B and 1C. Thus, as shown in FIG. 1D, a color filter 14c is formed in the region P2, and a color filter 15c is formed in the first region P3. As a result, a step coverage d occurs between the color filters 13c, 14c, and 15c, thereby causing a similar step coverage in an alignment layer 16, which is subsequently formed on the color filters 13c, 14c, and 15c. Accordingly, when rubbing the alignment layer 16, the alignment layer 16 corresponding to the step coverage d is not rubbed, thereby causing light leakage and reducing image quality.